Document scanners convert a visible image on a media object, such as and not by way of limitation, a document, photograph or a transparent media, into an electronic form suitable for copying, storing and processing by a computer. A document scanner may be a stand-alone device or integrated with a copier, a facsimile machine, a digital sender, or a multifunction device. Documents, or media objects, to be scanned may generally be classified as either transparent or opaque.
For scanning opaque media, light is reflected off an image on the surface of the document onto a photosensitive device by a process referred to as a reflective scan. The photosensitive device converts received light intensity into one or more electric signals. Transparent media are scanned by passing light therethrough, rather than reflecting the light off, the media. The transmitted light is received by an optics system and directed onto the photosensitive device. Transparent media may include either positive or negative images.
Document scanning systems operable to scan both transparent and opaque documents are available. Some conventional scanners include a separate light source to backlight the image on the transparent media.
In conventional scanner systems, the light projected onto the transparent media is only focused on a center section of the photosensitive device. Distal sections on both sides of the center section are typically unused for the most common transparent media object sizes.